The common electric sockets currently widely used to hold incandescent light bulbs have a number of concave threads in a metallic shell. Similarly, the bases of incandescent light bulbs presently employed with these sockets, have an outer metallic shell with corresponding convex threads that fit the concave threads in the sockets for the purpose of securing the bulbs in the sockets. Generally these bulbs are inserted and removed by hand.
The current standards for the manufacture of such bases require, amongst other things, a sufficient number of turns of thread to ensure that the bulb is secure in the socket. Due to the limited amount of rotation of the wrist, it requires a number of repeated movements of grasping and turning to insert and secure or release and remove a bulb manufactured within these standards.
If the number of threads on the base of the bulb can be greatly reduced to leave a smooth cylindrical portion, starting at the end that is to be first inserted, then the bulb can be inserted in the socket and removed with fewer turns. The bayonet type bulb in current use accomplishes this but it cannot be used with a threaded socket.
The prior art for threaded bases contemplates a short unthreaded portion for the purpose of facilitating the alignment of the bulb within the socket. But, the number of threads must be greatly reduced to substantially reduce the amount of turning. Merely reducing the number of threads in order to reduce the amount of turning is not sufficient.
If most of the thread is removed an alternative must be provided in place of the missing thread, to secure the bulb base in the socket. This invention combines the removal of all but a small portion of thread with the use of a thread that enlarges or increases in radius or both, to supplement the thread in securing the base in the socket.
The purpose of the invention is to make it possible to insert and remove the bulb with a minimum amount of turning while at the same time ensuring that electrical contact is made and that the bulb is secure.